The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Vehicles employ generators that are driven by a belt coupled to the vehicle engine to generate electrical power. Automotive electrical generators typically employ an AC synchronous machine with three-phase or multi-phase stator windings, a DC excitation winding on a claw-pole rotor, a voltage regulator and a diode bridge rectifier to produce a DC output. The excitation current of the synchronous machine is controlled by the voltage regulator to regulate the DC output voltage of the generator. Permanent magnets have been employed sometimes in the claw-pole device to increase the power output and efficiency of the generator for a given generator.
High efficiency generators usually employ shaped conductor stator windings to reduce copper losses, thinner stator laminations to reduce iron losses, low friction bearings, a laminated rotor construction and permanent magnetic excitation.
As mentioned above, known generator assemblies typically employ a diode bridge to convert the AC current to a DC current where the diodes conduct depending on the propagation direction of the current through the three-phase coils or the multi-phase coils.
The three-phase diode bridge rectifier converts an AC current to a DC current, where the diodes conduct depending on the propagation direction of the current through the three-phase coils or the multi-phase coils. A three-phase machine generally requires six diodes and a n-phase machine generally requires a number of diodes two times the number phases (n). Known generator systems include an active bridge rectifier employing low on-resistance switches, such as MOSFET switches, for converting the AC current from the machine to a DC current.
In known high efficiency generators with an active bridge rectifier the phase angle between the phase voltage and current is fixed, and accordingly the maximum output current/power is also fixed for a given generator speed and output voltage.